linux-kernel - Re: [PATCH 08/13] mm: remove the mask variable in hmm_vma_walk_hugetlb

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5f8e6310-5e97-3e57-bfbf-5eef553b4d91@nvidia.com>
Date:   Tue, 30 Jul 2019 18:01:11 -0700
From:   Ralph Campbell <rcampbell@...dia.com>
To:     Christoph Hellwig <hch@....de>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Felix Kuehling <Felix.Kuehling@....com>
CC:     <linux-mm@...ck.org>, <nouveau@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <amd-gfx@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/13] mm: remove the mask variable in
 hmm_vma_walk_hugetlb_entry


On 7/29/19 10:51 PM, Christoph Hellwig wrote:
> The pagewalk code already passes the value as the hmask parameter.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   mm/hmm.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index f26d6abc4ed2..88b77a4a6a1e 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -771,19 +771,16 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   				      struct mm_walk *walk)
>   {
>   #ifdef CONFIG_HUGETLB_PAGE
> -	unsigned long addr = start, i, pfn, mask;
> +	unsigned long addr = start, i, pfn;
>   	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>   	struct hmm_range *range = hmm_vma_walk->range;
>   	struct vm_area_struct *vma = walk->vma;
> -	struct hstate *h = hstate_vma(vma);
>   	uint64_t orig_pfn, cpu_flags;
>   	bool fault, write_fault;
>   	spinlock_t *ptl;
>   	pte_t entry;
>   	int ret = 0;
>   
> -	mask = huge_page_size(h) - 1;
> -
>   	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
>   	entry = huge_ptep_get(pte);
>   
> @@ -799,7 +796,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   		goto unlock;
>   	}
>   
> -	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
> +	pfn = pte_pfn(entry) + ((start & hmask) >> PAGE_SHIFT);

This needs to be "~hmask" so that the upper bits of the start address
are not added to the pfn. It's the middle bits of the address that
offset into the huge page that are needed.

>   	for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
>   		range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
>   				 cpu_flags;
>